1. Field of the Invention
The present invention is a motor of rotor with built-in permanent magnet, especially refer to a rotor which has no flux-barrier holes, and can effectively prevent phenomena of short-circuiting of magnetic flux.
2. Background of the Invention
As science is advanced day by day, the needs of normal life tend to short, light, thin and small products; the improvement of general mechanical mechanism is toward to high efficiency. The design of traditional motor torque of surface mount motor (T=Pn×φa×Ia, where Pn is pole number, φa is magnetic flux on d-axis, Ia is electric current on d-axis) is not suitable to electrical vehicles and compressors of refrigeration and air condition fields. Thus, adding an permanent magnet on rotor to promote total torque of traditional motor device, thus the total torque (T=Pn[φa×Ia+0.5(Ld−Lq)×Id×Iq], where φa×Ia is magnetic torque producing from permanent magnet of rotor, 0.5(Ld−Lq)×Id×Iq is reluctance torque producing form inductance difference of axes d and q) is with both magnetic torque and reluctance torque. Thus, under same volume condition, the motor of rotor with built-in permanent magnet which output torque and running efficiency are better than the traditional surface mount motor with magnetic torque. In another words, under same output torque condition, the volume of motor of rotor with built-in permanent magnet is smaller than the volume of the traditional motor with magnetic torque.
Please refer to FIG. 1A, which is sectional structure view of a 4-pole motor of rectangular piece permanent magnet in prior art. Wherein, the motor of rotor with rectangular piece permanent magnet comprises of: a annular stator 1 and a rotor 2. A cylindrical capacity with suitable diameter is set in the annular stator 1, and its circumference surface is with teeth 11 and openings 12. Each tooth 11 and each slot 12 are interlaced each other. There are some wires winding around slot 12. The rotor 2 is a cylindrical structure set in the cylindrical capacity, and there is an air gap 13 between rotor 2 and the circumference surface of cylindrical capacity. Rotor 2 further includes a cylindrical rotor core 20, and four rectangular openings 21 which are set surrounding the rotor core 20. Four relative rectangular solid permanent magnets 22 just insert and match into four rectangular openings 21. The arrangement for four rectangular solid permanent magnets 22 and four rectangular openings 21 is interlaced. When annular stator 2 is electrified, slot 12 produces magnetic forces in order for rotating annular stator 2. Four rectangular piece permanent magnets 22 are easily made and thus manufacturing cost is lower, but the arrangement causes serious magnetic flux leakage and cogging phenomena. Flux leakage lowers down effective torque and motor efficiency. Cogging phenomena increases motor cogging torque, and vibration and noise are both increased as well. Therefore, several flux-barrier holes 211 are drilled on two ends of each rectangular piece 21 in prior art, but the cost is higher, and solving the aforesaid shortcomings is not much (showing as FIGS. 1B and 1C). Besides, because of the flux-barrier holes 211, permanent magnet 22 is hardly fixed when permanent magnet 22 inserting into rectangular openings 21, and thus viscose is a need. Obviously, motor assembly becomes very complicated.
Please refer to FIG. 2, which is sectional structure view of motor of arc piece permanent magnet in prior art. Wherein, four arc piece pieces 23 are set surrounding rotor core 20, and four relative arc piece permanent magnets 24 are inserted and matched into the four arc piece pieces 23. The arrangement for four arc piece permanent magnets 24 and four arc piece pieces 23 is interlaced. Generally, for producing greater reluctance torque, the arrangement in rotor core 20 is that top arc of arc piece 23 is toward to rotor center of motor. Two ends of each arc piece 23 are toward to contour of rotor core 20. The figures of the two ends of each arc piece 23 are based on arc curvature of rotor core 20. Although the design highly decreases magnetic flux leakage and promotes output torque, the arc curvature of arc piece permanent magnet 24 is complicate, and it is not easily formed in manufacturing. The cost of arc piece permanent magnet 24 for easily inserting and matching into arc piece 23 with no loose is much higher than the cost of rectangular piece permanent magnet, further, cogging torque is also bigger to simply produce vibration.
As a conclusion of aforesaid prior arts, the shortcomings for them cannot be solved one by one, thus the present invention will be described as below to figure out the defects in prior art.